there is really only 3rd ave down there. There are days where it can be buttery but only as a result of equalized tides and thermal winds. I have heard there is a spot up from the upper launch that is protected a bit more but dont know if the water is glassy or not. nothing will come close to sherman's butter behind the islands.

under of the center of the Golden gate bridge yesterday was smooth as butter.. and i mean like riding behind the island at Sherman with 25mph winds.
It was super sketchy getting out but absolute butter out in the middle